Flexible and rigid tubing may have formed ends for use in coupling the tube to a fitting or to another tube. Flexible tubing may, for example, have flared ends to be joined to a flexible or rigid tube or fitting. A flared tube may be joined without a bushing and/or a nut. The inner diameter of the flare may be sized to accept and be joined to the outer diameter of a tube or fitting. The end of rigid tubing may be formed into a flare or flange.
Flexible tubing ends may be formed into flares using “cold flare” tools or heated flare tools. Cold flare tools use pressure alone to shape a tube end into a flare. Conventional heated flare tools unevenly heated the end of a tube and may use a flare form inserted into the tube to form a flare. Shaped tube end flares made by these methods typically lose their shape, due to the elastic memory of the tubing, at normal operating temperatures and pressures. As a result, the connections to the flared ends often developed leaks over time.
U.S. Pat. No. 7,604,472 B2, hereinafter referred to as the '472 patent, describes a method and apparatus for forming flared tube ends, the entire contents of which are incorporated herein by this reference. As described at column 1, line 66 to column 2, line 14 of the '472 patent, a flared tube end may be used in coupling a flexible tube to a tube, pipe or fitting. FIG. 1 of the '472 patent illustrates an exemplary embodiment of a flexible tube 1 with a flared end 2 to be fitted to a mating portion 3. A nut 4 may be provided to mate with threads 5 on the mating portion 3 to secure the fitting. The inner profile 6 of the flared end 2 of the flexible tube 1 may be formed to conform to the profile of the outer surface 7 of the mating end 8 of the mating portion 3. The flexible tube may be selected so that the inner diameter 9 of the flexible tube 3 matches the inner diameter 10 of the mating portion 3 where the interior surface 11 of the flexible tube meets the interior surface 12 of the mating portion 3, which may provide surface continuity along the interior surfaces of the fitting and may reduce the likelihood of leaks or fitting failure. In an exemplary embodiment, the flare is at a 45 degree angle with a 0.060 inch radius. The method and system disclosed in the '472 patent solved the problems of leakage, and provided flared flexible tubing ends which provide excellent performance against connection leakage.